After having looked at Scripture, one can find help in preaching the Biblical message from the next source for Biblical Preaching is History. This includes both an understanding of the history of the empires and people who interacted with the Biblical characters. This would include Egypt, Babylon, Persia, Greece, and Rome. Such an understanding can provide background for understanding the Biblical text.
Not only an understanding of the history of those cultures, but also history down through the ages can help to illustrate important truths. You may find something in World History. Maybe Western Civilization can provide narratives that illustrate the Bible.
One can also use African and African American history to illuminate truths. Take someone like Dr. Frederick D. Haynes in Dallas Texas. He often uses Black characters and history to illustrate the points that he is preaching. Use of those illustrations gives his preaching of sermons a decided “Black” feel.
One should also make use of denominational history. In my opinion, many people of all denominations do not make use of their own denominational history in their preaching. In addition, look at other histories. There are stories in the Methodist tradition about John Wesley that anyone can use, the Methodists don’t “own” John Wesley. Likewise in other denominational groups there is a wealth of information that can help.
A good place to find information is the web. Make a regular practice of searching such places as Wikipedia and Google for history. Store your findings in a file. Then refine the file for use.